#include<bits/stdc++.h>
#define i64 long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

void solve()
{
    i64 a, b;
    cin >> a >> b;
    for (i64 i = a + 1; i < b; i++)
    {
        if (__gcd(a, i) == 1 && __gcd(i, b) == 1)
        {
            cout << i << endl;
            return;
        }
    }
    cout << -1 << endl;
}

signed main()
{
    // ios::sync_with_stdio(0);
    // cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}